CRP, a component of serum that increases dramatically in inflammation, has been shown to consist of five protomers arranged in cyclic symmetry at the vertices of a regular pentagon. Human and rabbit CRP measure 11 nM in width and the individual promoters are 3.8 nM in diameter. A molecular weight of 23,700 can be calculated. Pentameric molecules are so rare that a new class of molecules called PENTRAXINS has been proposed. BIBLIOGRAPHIC REFERENCE: Osmand, A.P., Friedenson, B., Gewurz, H., Painter, R.H., Hofman, T. and Shelton, E.: Characterization of c-reactive protein and the complement component Clt as homologous proteins displaying cyclic pentameric symmetry (pentraxins). Proc. Nat. Acad. Sci. USA 74: 739-743, 1977.